Abstract
We present Stokes I Zeeman splitting measurements of sunspots using the highly sensitive (g = 3) Fe i line at λ = 1.5649 μm. The splittings are compared with simultaneous intensity measurements in the adjacent continuum. The relation between magnetic field strength and temperature has a characteristic, nonlinear shape in all the spots studied. In the umbra, there is an approximately linear relation between B 2 and T b, consistent with magnetohydrostatic equilibrium in a nearly vertical field. A distinct flattening of the B 2 vs T brelationship in the inner penumbra may be due to changes in the lateral pressure balance as the magnetic field becomes more horizontal; spatially unresolved intensity inhomogeneities may also influence the observed relation.
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Kopp, G., Rabin, D. A relation between magnetic field strength and temperature in sunspots. Sol Phys 141, 253–265 (1992). https://doi.org/10.1007/BF00155178
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DOI: https://doi.org/10.1007/BF00155178